We report the effects of chemical doping on thermoelectric properties of metal-based thermoelectric materials Sn1−xMxCCo3 (M = Ag, In, Ge, Pb, Sb, Te, and Bi) with antiperovskite structure. Compared to parent compound SnCCo3, both Seebeck coefficient (S) and figure of merit (ZT) can be effectively enhanced by hole doping, while a decreased S and ZT appear in equivalent- and electron-doped SnCCo3. Among all the doped samples, the maximum ZT value of 0.045(1) is obtained in Sn0.95Ag0.05CCo3, which is about 50% larger than that of parent compound SnCCo3 (ZT ∼ 0.03). This enhanced ZT is mainly attributed to the increased S induced by locally modified density of states near Fermi level. In addition, our optimized ZT value (∼0.045, at 235 K) is relatively large compared with other typical low-temperature thermoelectric materials.